Clamping system for detachably assembling two pieces

ABSTRACT

A clamping system for detachably assembling two pieces. The clamping system includes a clamping device concentrically mounted in a receiving section which extends in a hollow shaft of one of the two pieces, when the two pieces are engaged. The clamping system further includes at least two clamping bodies which can move in opposite directions and an actuating device which actuates the clamping bodies. The clamping bodies can be engaged with an undercut clamping shoulder of the hollow shaft and disengaged therefrom, whereby a pressure force is applied between the flat surfaces of the two pieces to be assembled.

FIELD OF THE INVENTION

1. Background of the Invention

The present invention relates to a clamping system for detachablyconnecting two parts, such as is used for coupling a workpiece or toolcarrier, for example in the form of a tool base holder, to a manipulatorunit such as a spindle of a machine tool, or for coupling tool systemmodules to one another.

2. Discussion of the Background

In such clamping systems the objective is to clamp the parts to beconnected reliably and firmly against one another, thus ensuring exactpositional fixation of the parts to be connected relative to each othervia close-fitting engagement between the faces of a hollow shank of theone part and of a holding portion of the other part. The tightening orclamping of the two parts to be connected against one another isachieved by the fact that the hollow shank is pulled into the holdingportion against an undercut clamping shoulder formed in the hollow shankduring application of clamping members of a clamping device. In theprocess a pressing force is developed between plane faces of the partsto be connected, so that the two parts clamped against one another areprovided with exact axial and also radial positional fixation by thefirm connection between the close-fitting faces.

In more recent times there has been increasing acceptance of thehollow-shank clamping system, in which the hollow shank has eithercylindrical or tapered structure. In the joined-together condition ofthe two parts to be connected to each other, the clamping members usedfor clamping the parts against one another ensure not only that anadequate axial pressing force is developed but also that the hollowshank experiences a certain radial flaring, whereby the accuracy of fitbetween hollow shank and holding portion is additionally improved.

In conventional clamping systems according to the principle describedhereinabove, the assembly and disassembly of the clamping device in theholding portion provided therefor represents a special problem,.however, since the clamping system must also absorb the reactions to theclamping force in addition to ensuring exact axial and radial positionalfixation of the two parts to be connected.

From German Patent Application DE A 4220873, there is known a clampingsystem for detachably connecting two parts, which preferably arerotationally symmetric, of which one part has a preferably cylindricalor tapered hollow shank and the other part has a corresponding holdingportion for holding the hollow shank in accurately fitting relationship.There is provided a clamping device which is disposed concentrically inthe holding portion and which, in the joined-together condition of thetwo parts, extends into the hollow shank of the one part and is providedwith at least two clamping members which can move in opposite directionsas well as with an actuating device for driving the clamping members, bymeans of which device the clamping members can be synchronously movedinto and out of engagement with an undercut clamping shoulder of thehollow shank, whereby a pressing force is generated between plane facesof the two parts to be connected.

This clamping system is based on the principle described hereinabove ofclamping two parts to be connected by a clamping device having clampingmembers. In this clamping system the problem cited hereinabove is solvedby exact positional fixation of the parts to be connected, in that asupport member decoupled from the clamping members as regards assemblyis fixed interlockingly in the holding portion. The positionally fixedsupport member brings about bracing of the clamping members and thusindirectly absorbs the reactions to the clamping force. The indirectabsorption of the reaction via the support member as well as thefastening and positional fixation thereof can be achieved, however, onlyby additional fixing and fastening elements. Furthermore, specialassembly attachments are generally necessary.

In another known clamping system, as is described, for example, inGerman Patent DE C2 3807140, a plurality of loosely disposed or at leastnot distinctly fixed clamping elements must be nested interlockingly inthe holding portion. In this case an additional support member is indeedunnecessary, but the direct nesting of the clamping elements isassociated with considerable assembly complexity, since the individuallydisposed clamping elements are not distinctly fixed in assemblyposition. Accordingly, the clamping elements must be moved into aspecial assembly/disassembly position during assembly/disassembly.Additional components and assembly attachments are necessary for thispurpose also.

From German Utility Model DE U1 29518660 there is known a clampingsystem according to the preamble of the new claim 1.

A threaded sleeve, a clamping ring and a plurality of segmented bracingelements are necessary for fixation of the clamping-element halves inthe tool spindle. The head parts of the clamping-element halves aretherefore braced against the undercut clamping shoulder of the toolmandrel via a “mechanism” formed by the clamping ring and the bracingelements.

The object of the present invention is therefore to provide a clampingsystem for two parts to be connected, for example a tool system moduleand a machine tool spindle, which clamping system on the one handperforms adequately with a minimum of components and on the other handpermits simple, reliable and dimensionally stable coupling of the twoparts to be connected without the need for additional assembly orfastening attachments.

This object is achieved by a clamping system with the features of claim1.

According to the invention, the clamping elements are each provided in aregion between head and foot portions with a retaining portion, whichcan be brought into engagement with an undercut recess of the holdingportion.

Just as heretofore, therefore, the clamping members are still designedas head portions of elongated clamping elements disposed substantiallyparallel to the longitudinal or rotational axis of the holding portion.The clamping elements are constituents of the clamping device. The footportions of the clamping elements are inventively connected to oneanother such that the clamping device has substantially the form of aV-shaped or U-shaped split chuck or clamping fork.

These clamping elements can be connected to one another movably,interlockingly and frictionally or in one piece. By means of anactuating device the clamping members can be made to move in oppositedirections, or in other words to move toward or apart from one another.The inventive clamping system with such a predetermined arrangement ofclamping elements relative to one another therefore obviates the supportmembers which in conventional clamping systems are necessary for theclamping elements or clamping members.

This arrangement of the clamping elements also permits, withoutadditional fixing components, distinct axial as well as radial fixationof the clamping members relative to one another in both the clampedposition and detached position of the clamping system. The inventiveclamping system is therefore characterized by simple and compactstructure, which also permits reliable and dimensionally stable clampingof the parts to be connected without a plurality of loose components. Inaddition, the connection of the clamping elements in the mannerdescribed hereinabove creates a clamping device which, since it does notcomprise any loose parts, can be fixed in the holding portion withoutgreat mechanical complexity.

Since, moreover, a minimum of movable parts is present in the inventiveclamping system, only little friction is developed during movementthereof. In this way a relatively large clamping force is achievedbetween the two parts to be connected.

Further advantageous embodiments of the inventive clamping system aresubject matter of the dependent claims.

The clamping elements are preferably designed as the arms of a U-shapedclamping fork of one-piece construction. In such a configuration theclamping device therefor e comprises only the clamping fork and theactuating device, and so the number of necessary components is reducedto two components. The one-piece configuration of the clamping elementsin the form of a clamping fork further creates the possibility ofincreasing the clamping force between the two parts to be connected bybending stresses of the clamping fork. The clamping force is generatedby the spring tension of the clamping fork when the actuating device isreleased. This spring tension can be adjusted by appropriate forming inthe stress-free condition. The one-piece design of the clamping elementsin the form of an elastically deformable clamping fork also permitssimple assembly of the clamping device in the holding portion, sincethere is no need to dispose and fix a plurality of loose components.

It is also possible, however, to connect the clamping elements of theclamping device by an articulated joint which includes the foot portionsof the clamping elements, the axis of rotation of which joint isdisposed perpendicular to the longitudinal or rotational axis of theparts to be connected. This design provides substantially the sameadvantages as the one-piece design of the clamping elements.

The clamping device of the inventive clamping system is preferablyprovided in a region between head and foot portions with a radiallyoutwardly projecting retaining portion in the form. of a clampingshoulder, and by means of this retaining portion can be nested in anundercut recess of the holding portion. By virtue of this technicallysimple expedient the clamping device can be engaged with or disengagedfrom the recess of the holding portion synchronously with the movementof the clamping members or with the pivoting movement of the clampingelements, depending on whether the clamping members are engaged with ordisengaged from the undercut clamping shoulder of the hollow shank.Accordingly, therefore, axial fixation of the clamping device in theholding portion can be achieved without additional fixing elements.

In particular, the configuration of the recess in the form of a closedannular cross section does not represent any weakening of the nestingshoulder of the recess of the holding portion, as can occur inconventional clamping systems, for example due to countersunk portionsin the case of a bayonet fastener. Compared with the production of aplurality of recesses, which extend in the direction of rotation of thetool holder only over portions of the inside circumferential wall of theholding portion, the production of a single recess in the form of aclosed annular cross section additionally proves to be particularlysimple. Such a configuration has also proved to be advantageous withregard to assembly of the clamping device, since the clamping device canbe introduced: into the holding portion without any concern over itsangular orientation relative to the holding portion.

In order to achieve the highest possible pressing force between the twoparts to be connected, it has proved particularly advantageous toprovide each of the clamping members with one wedge face, whichcooperates with a mating wedge face provided on an undercut clampingshoulder of the hollow shank, this clamping shoulder preferably beingformed by a recess in the form of a closed annular cross section. Bymeans of this type of configuration, therefore, there can be created awedge-type mechanism, which is characterized by relatively highefficiency.

According to a further development of the inventive clamping system,there is provided a push-off attachment which is automatically actuatedor moved axially upon detachment of the engagement of the clampingmembers with the undercut clamping shoulder of the hollow shank. Axialactuation of the push-off attachment leads to separation of the twoconnected parts. In this case the forced movement of the clampingmembers upon detachment of the clamped engagement of the clampingmembers with the undercut shoulder can be utilized to generate apush-off force acting axially on the components to be separated.

According to the invention this is accomplished in simple manner by apush-off piston as part of the push-off attachment, which piston isdisposed in a central recess of the part supporting the hollow shank andwhich, when the engagement of the clamping members with the undercutclamping shoulder of the hollow shank: is detached, can presssynchronously with increasing force against a bracing face of the partsupporting the hollow shank. By virtue of the central disposition of thepush-off piston, therefore, a centrally acting, positive force isapplied on the part supporting the hollow shank, ultimately leading toseparation of the two connected parts. Because of the centrally actingforce on the part supporting the hollow shank, the jamming and faultygripping of the two parts that occur under some circumstances can alsobe prevented.

For this purpose it has proved advantageous to provide on the push-offpiston a tapered face over which the clamping members can travel upondetachment of the clamping system. A sufficiently large push-off forcebetween the parts can be generated with this simple “wedge-typemechanism”, and so even a firm connection produced by the fact that twoparts with tapered close-fitting faces have been clamped together . . .with the detachment of the engagement of the clamping members with theundercut . . . .

When the push-off piston and the clamping device are held in sealedrelationship in the corresponding recesses, preferably by sealing ringsdisposed in appropriate recesses, a coolant and lubricant canadditionally be supplied via the parts clamped against one another to,for example, a cutting tool clamped in the one part. The seal of thepush-off piston and of the clamping device can also be used to stabilizethese components, and so vibration-induced chattering noise can beprevented.

Accordingly, the inventive clamping system can be combined with acoolant and lubricant supply system. This coolant and lubricant supplysystem comprises in particular a channel portion which is formed in thepart supporting the holding portion, a channel portion which is formedin the part supporting the hollow shank, plus at least one line portionwhich bridges the clamping device and ensures fixation of its angularorientation. The line portion of the coolant and lubricant supply systemcan then ensure fixation of the angular orientation of the clampingdevice in the holding portion, and so further structural expedients orother fixation elements are not needed in this regard.

The line portion is preferably designed as a tube which is disposedbetween the parts to be connected, the end of this tube on thehollow-shaft side being held interlockingly and/or frictionally,preferably by sealed brazed joint, in a corresponding recess of thepush-off piston, the shank portion of this tube being guided movably,preferably in a manner sealed by a sealing ring, through a correspondingrecess in the connecting portion of the foot portions of the clampingelements, and the end of this tube on the holding-portion side beingheld in close-fitting relationship in a corresponding recess in the partsupporting the holding portion.

As already described hereinabove, the line portion or the tube can beused for fixation of the angular orientation of the clamping device inthe holding portion. The line portion or the tube is then disposedbetween the clamping members in such a way that the clamping memberspinch the line portion or the tube between them when the clamping systemis in detached position. This means that the coolant and lubricantsupply system is securely retained in the holding portion without theneed for additional fixation elements when the clamping system is indetached position.

Preferably the parts to be connected are designed as rotationallysymmetric parts and the pressing faces of the parts to be connected aredesigned as radial annular faces. This contributes decisively to asimple and thus low-cost clamping system.

In order to achieve the most intimate possible connection between thetwo parts to be connected and thus to keep the torque-transfer losses assmall as possible, the close-fitting faces between hollow shank andholding portion preferably have the form of tapered faces.

The drive of the actuation device is provided preferably via a radialopening oriented perpendicular to the longitudinal or rotational axis ofthe two parts to be connected, preferably via a radial bore, into whicha tool, in the form, for example, of an Allen key, . . . from outside.

Furthermore, in a preferred embodiment of the clamping system, theactuating device for actuating the clamping members is constructed as atightening screw with a head portion and a threaded portion, the headportion being disposed in a correspondingly configured recess of the oneclamping member and the threaded portion in a corresponding threadedbore of the other clamping member.

An advantageous embodiment of the tightening screw has been found to beone in which the threaded portion of the tightening screw has aleft-hand threaded portion and a right-hand threaded portion, of whichone is disposed in the threaded bore of the other clamping member andthe other is disposed in a nut functioning as the head portion, the nutbeing disposed in the correspondingly configured recess of the oneclamping member. The advantage of this embodiment is that, by virtue ofthe left-hand/right-hand thread of the tightening screw, relativelysmall turning movements are necessary in order to bring about arelatively large “stroke” of the clamping elements; furthermore, the nutfunctioning as the head portion is subjected only to tension and thusdoes not undergo any frictional wear.

In addition to a rotationally symmetric configuration of the two partsto be connected, it has proved advantageous to make the clamping devicealso from a cylindrical part, so that the clamping elements and theclamping members have an arcuate outside face and the foot portion ofthe clamping elements has a cylindrical outside face.

As regards a simple possibility for limiting the clamping stroke of theclamping members, it has proved to be particularly advantageous when theclamping elements can bear against the inside circumferential wall ofthe recess of the holding portion while the two parts to be connectedare in the tightened or clamped-together condition. In this way amaximum permissible clamping stroke of the clamping elements and thus ofthe clamping members can be safely maintained without additionallimiting elements or stops.

In order to shorten the axial overall length of the clamping device andthus of the clamping system as a whole by a structurally simple means,it is further advantageous to provide each clamping element on the sideof its foot portion with at least one notch which reduces the crosssection. Thereby the force necessary to pinch the clamping elementstogether can be reduced and, as a positive consequence thereof, thenecessary “lever-arm length” of the clamping elements can beconsiderably shortened.

Further advantageous features of the present invention will becomeapparent from the description hereinafter, wherein a preferred practicalexample of this invention will be explained in more detail withreference to a schematic drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 a schematic axial section—in partly cutaway view—of the inventiveclamping system according to the preferred practical example with thetwo parts to be connected in clamped-together condition;

FIG. 2 is a schematic axial section—in partly cutaway view—of theinventive clamping system according to the preferred practical examplewith the two parts to be connected in clamped-together condition;

FIG. 3 is a cross section through the inventive clamping system in FIG.1 along line “III—III”;

FIG. 4 is a cross section through the inventive clamping system in FIG.2 along line “IV—IV”;

FIG. 5 is a schematic view—partly cutaway—of a clamping device of theinventive clamping system;

FIG. 6 is a cross section through the clamping device along line “VI—VI”in FIG. 5;

FIG. 7 is a schematic top view of the clamping device in FIG. 5;

FIG. 8 is a schematic view—partly cutaway—of a coolant and lubricantpush-off attachment;

FIG. 9 is a schematic view of a push-off piston viewed in a directioncorresponding to arrow “IX” in FIG. 8;

FIG. 10 is a cross section of the holding portion of the tool holderaccording to a second practical example;

FIG. 11 and FIG. 12 are cross sections through the clamping device alongline XI—XI in the detached condition of the clamping system according tothe second practical example;

FIG. 13 is a cross section through the clamping device along lineXIII—XIII in the clamped condition of the clamping system according tothe second practical example;

FIG. 14 is a schematic axial section—in partly cutaway view—of theinventive clamping system according to a third practical example withthe two parts to be connected in clamped-together condition;

FIG. 15 is a schematic axial section—in partly cutaway view—of theinventive clamping system according to the preferred practical examplewith the two parts to be connected in clamped-together condition;

FIG. 16 is a cross section through the inventive clamping system in FIG.14 along line “XV—XV”;

FIG. 17 is a cross section through the inventive clamping system in FIG.16 along line “XVII—XVII”;

FIG. 18 is a side view—partly cutaway—of the clamping device of theinventive clamping system according to the third practical example;

FIG. 19 is a top view—partly cutaway—of the clamping device of theinventive clamping system according to the third practical example; and

FIG. 20 is a front view of the clamping device of the inventive clampingsystem according to the third practical example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 there is illustrated a part denoted by reference numeral20 and referred to hereinafter as the tool, for example a tool systemmodule in the form of a tool base holder, and a part denoted byreference numeral 22 and referred to hereinafter as the tool holder, forexample a spindle of a machine tool. It must be emphasized here and now,however, that the clamping system to be described in more detailhereinafter relates to the interface of two parts to be connected and istherefore qualified for all practical applications in which it isnecessary to connect two parts to one another in centered and detachablerelationship.

In FIG. 1 and FIG. 3, tool 20 and tool holder 22 are shown in theclamped-together condition or tightened condition, in which a radialannular face 24 of tool 20 is pressed against a radial annular face 26of tool holder 22, while at the same time a hollow shank 28 of tool 20is held in centered relationship in a corresponding recess 30 of aholding portion 32 of tool holder. 22.

FIG. 2 and FIG. 4 show tool 20 and tool holder 22 in the joined-togetherbut not clamped-together condition. Even in this condition, hollow shank28 of tool 20 is already held in recess 30 of tool holder 22. Betweenthe two radial annular faces 24, 26, however, there is formed a planegap, since tool 20 becomes stopped against a push-off piston 82 of apush-off attachment 80 to be described in more detail hereinafter.

In the practical example shown in FIG. 1 and FIG. 2, the close-fittingfaces between hollow shank 28 and recess 30 are formed by tapered faces.It is equally possible, however, to provide for centering of hollowshank 28 in recess 30 via cylindrical faces.

Although the intimate connection between the tapered close-fitting facesalready ensures that tool 20 and tool holder 22 are secured againstrelative turning when tool 20 and tool holder 22 are in clamped-togethercondition, additional security against relative turning between tool 20and tool holder 22 can also be achieved by, for example, at least onetang block, which engages in a corresponding end recess either of thehollow shank or of the holding portion.

In the practical example shown in FIG. 1 and FIG. 2, parts 20, 22 to beconnected as well as hollow shank 28 and the recesses formed in theseparts, such as recess 30, have rotationally symmetric geometry. It mustbe emphasized, however, that the invention is not limited merely to suchgeometry.

The inventive clamping system must be capable of clamping parts 20, 22to be connected firmly against one another in predesignated radial andalso axial position. A further feature essential to the invention,besides a minimal number of components and simple assembly capability,is easy detachability of the connected parts in combination with shortstroke distances. For this purpose the inventive clamping system has thefollowing structure:

Hollow shank 28 is provided on the inside with a radially orientedundercut clamping shoulder 34. Clamping shoulder 34 is formed by a wedgeface of an annular recess of hollow shank 28, this face being directedtoward the tool holder. During actuation of the clamping system, wedgefaces 36 of two clamping members 38 can bear against clamping shoulder34, in order to bring about, preferably with force conversion, firmclamping of tool 20 against tool holder 22.

In an axial guide recess 31 of holding portion 32 of tool holder 22there is disposed a clamping device 39, which at the bottom of the guiderecess bears via a sealing ring against the inside circumferential wallof guide recess 31. As can be seen in FIG. 5 and FIG. 6 in particular,clamping device 39 comprises a U-shaped clamping fork of one-piecestructure and an actuating device in the form of a tightening screw 42.The clamping fork is preferably made from a cylindrical member, as canalso be recognized from the diagram according to FIG. 6. FIG. 7 shows atop view of the clamping fork. It comprises two clamping elements 40,which are oriented substantially parallel to longitudinal or rotationalaxis 43 of tool holder 22, and which are formed by the arms of theU-shaped clamping fork. Clamping elements 40 preferably have an arcuateoutside face corresponding to the circumferential face of axial guiderecess 31 of holding portion 32. The head portions of the two clampingelements 40 form clamping members 38, which are equipped with wedgefaces 36. As can be seen in FIGS. 5 and 6 and will be described in moredetail hereinafter, tightening screw 42 is connected interlockingly andfrictionally with the two clamping members 38. Clamping elements 40 areconnected to one another in one piece at their foot portions 41,preferably in the form of a “material articulated joint”. According tothe present invention, however, it would also be possible to design thefoot portions of clamping elements 40 as constituents of an articulatedjoint connecting clamping elements 40.

Between clamping members 38 and articulated joint 41 there are providedon clamping elements 40 retaining portions 44, with which clampingdevice 39 can be nested in an undercut recess 46 of axial guide recess31 of holding portion 32 and thus can be fixed axially in tool holder22. Undercut recess 46 has a closed annular cross section. Since theclamping fork, as mentioned hereinabove, has a cylindrical outsidecontour, retaining portions 44 are accordingly disposed in diametricallyopposite relationship on clamping elements 40 and have the form ofradially projecting bracing noses or shoulder portions.

According to the diagram in FIG. 5 and FIG. 6, tightening screw 42 has aspherical head portion 52, a neck portion 53 adjoining head portion 52and having diameter smaller than that of the head portion, an annularportion 54 following neck portion 53 and having diameter larger thanthat of neck portion 53, a shank portion 55 adjoining annular portion 54and having diameter smaller than that of a threaded bore 62 of upperclamping member 38 in FIG. 5, as well as a threaded portion 56 whichadjoins shank portion 55 and is held in threaded bore 62 of upperclamping member 38 in FIG. 5. Threaded portion 56 of tightening screw 42has a recess 60 indicated by broken lines, preferably a hexagon socket.

Lower clamping member 38 in FIG. 5 has a concave recess 57 correspondingsubstantially to the contour of spherical head portion 52, this recessbeing limited in the direction of the upper clamping member by a bottomportion 58, which has a height H (FIG. 6) corresponding approximately tothe axial length of neck portion 53. Bottom portion 58 is provided witha slot 59, which starts from its end side, or in other words from theleft side in FIG. 5, and which has a width B (FIG. 6) somewhat largerthan the diameter of neck portion 53. Tightening screw 42 can thereforebe inserted with its neck portion 53 into slot 59, as is shown, forexample, in FIG. 5 and FIG. 6, in which case bottom portion 58 of recess57 is held with clearance between head portion 52 and annular portion54.

Upper clamping member 38 in FIG. 5 has a threaded bore 62, in whichthere is held threaded portion 56 of tightening screw 42. Threadedportion 56 is therefore functionally engaged with clamping member 38.

As already mentioned hereinabove, tightening screw 42 is connected tothe two clamping members 38 of clamping device 39. Thus, when tighteningscrew 42 is turned, it brings about pivoting movement of clampingelements 40 around an imaginary axis of rotation (not illustrated)oriented perpendicular to axis 43 of tool holder 22. As illustrated inFIGS. 1 and 2, turning of tightening screw 42 is achieved by a tool 63introduced radially from outside in a direction substantiallyperpendicular to longitudinal or rotational axis 43 of tool holder 22,the said tool preferably having the form of an Allen key, which isintroduced through a radial opening 64 in holding portion 32 of toolholder 22 on the one hand and through a radial opening 66 in hollowshank 28 of tool 20 on the other hand into the aforesaid recess 60 oftightening screw 42.

From FIG. 1 and FIG. 2 it is further apparent that a rotational axis 70of tightening screw 42 is substantially aligned with the axes of radialopenings 64, 66. Radial openings 64, 66 are preferably designed asbores.

When tightening screw 42 is turned to the right, it leads to synchronousmovement of clamping members 38 apart from one another and thus toclamping of tool 20 against tool holder 22. When tightening screw 42 isturned to the left, it leads to synchronous movement of clamping members38 toward one another and thus to detachment of the wedge-type surfaceconnection between wedge faces 34, 36 and thus of the connection of tool20 and tool holder 22. By virtue of the detachment of the clampingsystem, or in other words the movement of the two clamping members 38together as a result of the turning of tightening screw 42 to the left,there are generated in clamping elements 40 and in foot or connectingportion 41 bending stresses, which of course are relaxed once again whenthe clamping system is tightened, or in other words when clampingmembers 38 are moved apart from one another as a result of the turningof tightening screw 42 to the right, and which therefore support thestroke of clamping members 38 in radially outward direction as well asthe clamping of tool 20 against tool holder 22. The spring tension ofthe clamping fork can therefore be transformed to a clamping force forclamping the two parts 20, 22 against one another. By appropriateforming of the clamping fork in the stress-free condition, therefore, itis possible to increase the spring tension of the clamping fork and thusthe bending stresses generated when tightening screw 42 is turned to theleft.

The diagram in FIG. 5 makes it evident that the maximum extent to whichclamping members 38 can be pinched together as tightening screw 42 isbeing turned to the left is when the two clamping members 38 becomestopped against annular portion 54 of tightening screw 42. Byappropriate dimensioning of the axial length of shank portion 55,therefore, it is ensured that threaded portion 56 cannot becomedisengaged from threaded bore 62. In this fully pinched-togethercondition of clamping members 38, the engagement of wedge faces 36 oftightening screw 38 with undercut clamping shoulder 34 of hollow shank28 is released, and so tool 20 can be removed from the tool holder.

From the diagram according to FIG. 1 it is evident that clamping members38 can be moved apart from one another when tightening screw 42 isturned to the right only to the extent that they bear against the insidecircumferential wall of holding portion 32 of the tool holder. In thisway, even without a tool-dependent stop for limiting the clamping strokeof the clamping members, it is ensured that a maximum permissibleclamping stroke, beyond which threaded portion 56 of tightening screw 42would become disengaged from threaded bore 62 of clamping member 38,cannot be exceeded. Further turning of tightening screw 42 after themaximum permissible clamping stroke of clamping members 38 has beenreached is therefore prevented automatically by the fact that theclamping elements bear against the circumferential wall of the recess inthe holding portion.

According to the clamped position shown in FIG. 1, clamping members 38are pushed back via wedge faces 36 against the wedge face of clampingshoulder 34, thus becoming mutually braced against tightening screw 42.

In the clamped position of the inventive clamping system shown in FIG.1, the contact between wedge faces 34, 36 ensures that hollow shank 28of tool 20 tends to be flared, whereby the close-fitting contact betweenhollow shank 28 and recess 31 becomes even more intimate. In thisclamped condition, therefore, a frictional and nonpositive connectionexists between the close-fitting faces of hollow shank 28 and recess 30on the one hand and between wedge faces 34, 36 on the other hand,whereby clamping device 39 becomes fixed in its angular orientationrelative to tool holder 22.

Further constituents of the inventive clamping system constitute apush-off attachment as well as a coolant and lubricant supply system,which in this practical example are designed as one component and willtherefore be referred to hereinafter as C&L push-off attachment 80.

The structure of this C&L push-off attachment is illustrated inparticular in FIG. 8 and FIG. 9. C&L push-off attachment 80 comprisessubstantially a push-off piston 82 as well as two tubes 84, 86. Push-offpiston 82 is designed as a rotationally symmetric component with acentrally disposed projection 88 as well as two axial recesses,preferably bores 90, 92, as is evident from FIG. 9. Tubes 84, 86 arebrazed in sealed relationship into axial recesses 90, 92 of the partsupporting the hollow shank, and in the installed condition according toFIG. 1 or FIG. 2 they extend from push-off piston 82 into guide recess31 of holding portion 32 of tool holder 22.

As shown in FIG. 1 and FIG. 2, push-off piston 82 is disposed in sealedrelationship in a central recess 94 of tool 20, by means of a sealingring held in a corresponding annular groove on the outside circumferenceof push-off piston 82. As follows in particular from FIG. 3 and FIG. 4,a plane El connecting the central axes of tubes 84, 86 and includinglongitudinal or rotational axis 43 is turned by 90° relative to a planeE2 connecting clamping elements 40 and also including longitudinal orrotational axis 43. According to FIG. 1 and FIG. 2, tubes 84, 86 extendinto guide recess 31 of holding portion 32 of tool holder 22 viacorrespondingly disposed axial recesses 94, 96 of foot or connectingportion 41 of the clamping fork to correspondingly provided recesses 98,100 of tool holder 22. Whereas the shank portions of tubes 84, 86 areheld in easily movable relationship in axial recesses 94, 96 ofarticulated joint portion 41, they are held in close-fittingrelationship in axial recesses 98, 100 of tool holder 22, there beingprovided for sealing recesses 94 a , 96 a, in each of which there isheld a sealing ring, as shown in FIG. 6.

Axial recesses 94, 96 of the tool as well as axial recesses 98, 100 ofthe tool holder constitute channel portions of the coolant and lubricantsupply system. Tubes 84, 86 on the one hand have the function of lineportions communicating between the channel portions in tool 20 and toolholder 22 and bridging clamping device 39, and on the other hand providefurther fixation of the angular orientation of the clamping device inthe tool holder in addition to that created by the bracing of the tooland tool holder, by the fact that they are held in axial recesses ofarticulated joint portion 41 of clamping device 39. In this way relativeturning of the clamping device in the tool holder is prevented,especially in detached position of the clamping system.

As follows in particular from FIG. 4, the two clamping members 38 indetached position of the clamping system pinch the two tubes 84 and 86in such a way that C&L push-off attachment 80 is prevented by simplemeans from falling out when the clamping system is in detached position.

Push-off piston 82 of C&L push-off attachment 80 has a centralprojection 88 with a tapered face 102 on the side directed toward thetool holder and especially clamping members 38. When the engagement ofwedge faces 36 of clamping members 38 with the wedge face provided onundercut clamping shoulder 34 is detached by turning tightening screw 42in appropriate direction, clamping members 38 move radially inwardtoward one another. The functional contact between wedge faces 36 andclamping shoulder 34 is gradually released. At the same time, clampingmembers 38 travel synchronously over tapered face 102 of push-off piston82. When tightening screw 42 is turned further, the radially actingforce applied by tightening screw 42 on clamping members 38 istransformed to an axially directed force acting on push-off piston 82,whereby this is pushed with increasing force against a bracing face 104of central recess 94 of tool 22, so that a centrally acting, positiveforce is applied on the tool. In this way clamping members 38 becomesynchronous with the constituent of a wedge-type mechanism, with whichhollow shank 28 can be forced out of holding portion 32, while push-offpiston 82 is braced against bracing face 104. This leads accordingly toautomatic separation of the connection created between tool and toolholder by the engagement of wedge faces 36 of clamping members 38 withundercut clamping shoulder 34. Since the push-off piston is centrallydisposed, symmetric force relationships can be achieved very easily forthe push-off process, and so reliable separation of the two parts 20, 22can be achieved even in the case of the most intimate adhesion betweentapered centering faces on the outside face of the hollow shank on theone hand and on the sides of recess 30 of holding portion 32 on theother hand.

Assembly/disassembly of the tool on/from the tool holder as well as themode of operation of the inventive clamping system will be described inmore detail hereinafter, assuming an initial condition in which allcomponents, meaning the tool, the tool holder and the clamping deviceconstitute individual parts, or in other words are separated from eachother.

The first step of assembly of the tool on the tool holder is to pinchclamping members 38 together. To do so, a suitable tool 63, which in theexplained practical example is an Allen key, is first introduced intorecess 60, which in the case of this practical example is a hexagonsocket, of tightening screw 42 and then turned to the left. Of course,the tightening screw must already have been inserted beforehand into thecorresponding recesses 62, 57 of clamping members 38, as illustrated inFIG. 5 and FIG. 6. The leftward turning of tightening screw 42 causesthe two clamping members 38 to move toward one another, until upperclamping member 38 in FIG. 5 bears against annular portion 54 oftightening screw 42, which is securely retained in lower clamping member38. In this condition, retaining portions 44 of clamping elements 40 canbe fitted into a circle having a diameter corresponding approximately tothat of recess 31 of holding portion 32 of tool holder 22; in any case,retaining portions 44 are not permitted to hinder the insertion of theclamping device into tool holder 22 as described hereinafter. With thepinching together of clamping members 38 in the manner describedhereinabove, bending stresses are generated in the clamping fork, or inother words in clamping elements 40 and in connecting portion 41 inparticular, which stresses are relieved once again when the tighteningscrew is subsequently turned to the right and which can therefore beused positively on the one hand for the radial stroke of the clampingmembers and on the other hand for bracing the tool with the tool holder.

Even in the case of a clamping device in which the clamping elements areconnected to one another by an articulated joint, bending stresses canbe generated by appropriate configuration of the foot portions formingthe articulated joint.

Since the clamping elements are connected to one another at their footportions and thus are moved radially outward in opposite directions inany case when the tightening screw is turned to the right, it is notabsolutely necessary, however, that the radial stroke of the clampingmembers be assisted by bending stresses generated beforehand when theclamping elements were pinched together. It is self-evident that thebracing or mutual clamping of the tool against the tool holder can alsobe achieved merely by the force applied radially to clamping members 38by virtue of actuation of tightening screw 42.

In the pinched-together condition of the clamping fork, clamping device39 can be introduced into guide recess 31 of holding portion 32 of toolholder 22, as can be seen from FIG. 2 and FIG. 4.

Clamping members 38 are then moved radially outward by turningtightening screw 42 to the right by means of tool 63 inserted via radialopenings 64 and 66 of tool 20 and tool holder 22 into recess 60 oftightening screw 42, whereby the bending stresses generated whenclamping members 38 were pinched together are relieved. As clampingmembers 38 or clamping elements 40 move apart from one another,retaining portions 44 simultaneously engage in recess 46 of holdingportion 32, thus achieving axial fixation of clamping device 39 in guiderecess 31 of holding portion 32 of tool holder 22. This condition isevident from the diagram in FIG. 1 and FIG. 3.

C&L push-off attachment 80 can now be introduced into tool holder 22 andits angular orientation adjusted in the manner evident from the diagramin FIG. 1 and FIG. 3. Once C&L push-off attachment 80 has been correctlypositioned, tubes 84, 86, which extend through the axial recesses offoot or connecting portion 41, bring about fixation of the angularorientation of clamping device 39 in guide recess 31 of holding portion32 of tool holder 22.

By turning tightening screw 42 to the left, clamping members 38 are thenpinched together once again until they bear against tubes 84, 86, asillustrated in FIG. 2 and FIG. 4. From the diagram in FIG. 4 it followsin particular that upper clamping member 38 is prevented from becomingstopped against annular portion 54 of tightening screw 42 in thiscondition by the fact that it bears against tubes 84, 86. Consequentlyretaining portions 44 are still engaged, albeit only partly, with recess46 of guide recess 31 of holding portion 32 of tool holder 22. This issufficient to prevent clamping device 39 from falling out of recess 31,especially when tool holder 22 is in vertical position. As is furtherevident from FIG. 2, the portions of clamping elements 40 adjoiningclamping members 38 no longer bear over the full support length againstthe inside circumferential wall of recess 31. This condition correspondsto the detached condition of the clamping system, in which tool 20 canbe exchanged.

In the detached position of the clamping system, clamping members 38additionally bear against tapered face 102 of push-off piston 82 of C&Lpush-off attachment 80, as can be seen in FIG. 2.

In the detached position, tool 20 with its hollow shank 28 can beinserted into the corresponding recess 30 in holding portion 32 of thetool holder, as is evident in FIG. 2. When in detached position, tool 20becomes stopped against push-off piston 82, which itself bears in turnagainst clamping members 38. In the detached position, a plane gap inthe range of 1/10 mm remains between radial annular faces 24, 26 of tool20 and tool holder 22, because push-off piston 82 projects axially fromtool holder 22 when the clamping system is in detached position.

After insertion of tool 20 into corresponding recess 30 of tool holder22, actuating screw 42 is turned to the right, thus causing clampingmembers 38 to move radially apart from one another. As tightening screw42 is turned further, wedge faces 36 provided on clamping members 38become engaged with undercut clamping shoulder 34 of hollow shank 28 onthe one hand, while the end faces of clamping members 38 synchronouslybecome disengaged from tapered face 102 of push-off piston 82.Accordingly, further turning of tightening screw 42 leads to clamping oftool 20 against tool holder 22, whereupon the force directed radiallytoward the clamping members and applied on clamping members 38 by theaction of turning of the tightening screw and relaxation of the bendingstress caused during pinching together of clamping members 38 istransformed via the wedge-type mechanism between wedge faces 34, 36 intoan axial force directed toward tool holder 22, thus pulling tool 20 intothe recess of tool holder 22. Similarly, because tool 20 is pulled intotool holder 22, push-off piston 82 is pushed into holding portion 32 oftool holder 22. Because of the tapered close-fitting faces on hollowshank 28 and in the corresponding recess of tool holder 22, there isproduced slight flaring of holding portion 32, whereby firm bracingbetween tool 20 and tool holder 22 is obtained. Simultaneously,retaining portions 44 become completely engaged with correspondingrecess 46, leading to a tensile stress with increasing clamping force inthe regions of the clamping elements between clamping members 38 and theretaining portions. The clamped position of the inventive clampingsystem is shown in FIG. 1 and FIG. 3.

During clamping of tool 20 against tool holder 22, tool 20 pushed C&Lattachment 80 into tool holder 22, as mentioned hereinabove. Coolant andlubricant supply lines for the supply of coolant and lubricant to thetool are created via channels formed in tool 20, which supports hollowshank 28, and in the tool holder, as well as via tubes 84, 86.

Tool 20 is changed substantially in the reverse sequence. The initialcondition in this case is the clamped position shown in FIG. 1. Byturning tightening screw 42 to the left, clamping members 38 move towardone another, whereupon the engagement of wedge faces 36 of clampingmembers 38 with undercut clamping shoulder 34 of recess 30 of holdingportion 32 is relaxed on the one hand and clamping members 38 travelover tapered face 102 of push-off piston 82 on the other hand. By meansof these processes the bracing between tool 20 and tool holder 22 isrelaxed as tightening screw 42 is further turned, and at the same timetool 20 is pushed out of tool holder 22.

Naturally it is not necessary to remove the clamping device from toolholder 22 in order to change the tool; instead, it is sufficient tobring the clamping system into the detached position shown in FIG. 2.

As regards the permissible stresses in the components disposed in theflow of force from clamping system to tool to tool holder, the favorablecircumstance arises that clamping elements 40 of the clamping fork,which have limited cross section for structural reasons, are subjectedin clamped position of the clamping system to pure tensile stresses,whereas bending stresses prevail in the detached position of theclamping system. Since the loadability of the clamping elementsrepresents a limit for the achievable clamping force of coupling of thetool and tool holder, a maximum level of clamping force for given crosssection of the clamping elements can be achieved with pure tensileloading.

The necessary radial stroke of the clamping members for changing thetools, as well as the mechanical conversion of the radially appliedtightening-screw force into an axially acting clamping force can beachieved by taking advantage of the elastic deformation of the clampingfork, without additional movable interlocking parts in the clampingsystem. The friction in the clamping system is thereby reduced to aminimum, whereby a distinct increase of clamping force is achievedcompared with conventional clamping systems.

Compared with conventional clamping systems, the clamping systemaccording to the invention substantially comprises only threecomponents, namely the clamping fork, the tightening screw and the C&Lpush-off attachment. The detached position of the inventive clampingsystem is also its assembly position. Additional components and assemblyattachments are therefore unnecessary.

In the practical example described hereinabove, the clamping fork hastwo clamping elements, each with one clamping member. The presentinvention is not limited merely to such a configuration, however, butcan also be provided with more than two clamping members.

In the practical example described hereinabove, the clamping fork is ofone-piece design. Within the meaning of the present invention, however,it would also be conceivable to construct the clamping fork from two“hemispherical” clamping elements, which can be connected movably to oneanother at their foot portions via an articulated joint, the axis ofrotation of which is disposed perpendicular to the longitudinal orrotational axis of the holding portion. Similarly, the clamping elementscould also be connected to one another in rotationally fixedrelationship via an appropriate configuration of their foot portionsthat permits an interlocking and/or frictional connection. For example,the foot portions of the clamping elements could be designed as portionswhich are “hemispherical” relative to the axis of rotation of theholding portion, each being provided at the joint face directed towardthe other with a wedge-type toothing, which permits reliable clampingtogether of the two clamping elements.

FIG. 10, FIG. 11, FIG. 12 and FIG. 13 show a second practical example ofthe present invention. This second practical example differs from thefirst practical example substantially only in the axial fixation ofclamping device 39 in the holding portion. Thus only the differencescompared with the first practical example will be explained hereinafter.

Holding portion 32 of tool holder 22 is illustrated in longitudinalsection in FIG. 10. As follows from FIG. 10, holding portion 32 isprovided with an axial, central recess 120, which substantiallycomprises recess 30 for hollow shank 28, a recess 121 in the form of anelliptical cross section and cylindrical guide recess 31. In recess 121of elliptical cross section there is formed recess 46 in the form of aclosed annular cross section for nesting of retaining portions 44 ofclamping elements 40.

Recess 121 in the form of an elliptical cross section can be seen inparticular in FIG. 11, FIG. 12 and FIG. 13. FIG. 11 and FIG. 12correspond substantially to a cross section through the inventiveclamping system shown in FIG. 2 in joined-together condition, clampingdevice 39 together with clamping elements 40 being shown in differentangular orientations. FIG. 13 corresponds to a cross section through theinventive clamping system in clamped condition, as shown in FIG. 1.

On the basis of the diagrams in FIG. 11, FIG. 12 and FIG. 13,installation/removal of clamping device 39 in/from recess 120 of holdingportion 32 of tool holder 22 will be explained hereinafter.Assembly/disassembly of the tool on/from the tool holder takes placesubstantially in the same manner as in the first practical example, andso further explanations in this regard are unnecessary.

Installation of clamping device 39 begins firstly with pinching togetherof the clamping fork, or in other words clamping members 38 of clampingelements 40. This takes place in the same manner as was explained inrelation to the first practical example.

In the pinched-together condition of the clamping fork, clamping device39 can then be introduced axially into recess 120 of holding portion 32of tool holder 22, the angular orientation of the clamping devicerelative to tool holder 22 during introduction into recess 120 beingillustrated in FIG. 11. In this angular orientation, plane El isoriented perpendicular to a plane EB, which connects the foci of theelliptical cross section of recess 121 and includes longitudinal orrotational axis 43. Accordingly, clamping elements 40 of clamping device39 only have to be pinched together radially to the extent thatsubstantially cylindrical clamping device 39 can be introduced intoelliptical recess 121.

Whereas in the first practical example clamping members 38 are movedradially outward only by turning tightening screw 42 to the right inorder to be able to fix clamping device 39 axially in recess 120, in thesecond practical example clamping device 39 is merely turned around axisof rotation 43 by 90° relative to tool holder 22 after it has beeninserted completely into recess 121, or in other words is bearingagainst the bottom of guide recess. 31, so that plane El and plane EBare disposed in a common plane. In the process, the direction in whichthe clamping device is turned is immaterial. As shown in FIG. 12, suchturning of the clamping device has the consequence that retainingportions 44 are brought into engagement with undercut recess 46, and soclamping device 39 becomes axially fixed in holding portion 32 of toolholder 22.

After insertion of the tool into the tool holder, the clamping system isultimately brought into the clamped condition by turning tighteningscrew 42 to the right, as is known from the first practical exampleillustrated in FIG. 1.

Removal of clamping device 39 from recess 121 of tool holder 22naturally takes place in reverse sequence.

Accordingly, this second practical example differs from the firstpractical example only in the features of the axial fixation of theclamping device in the tool holder, which in this case takes placesubstantially in the manner of a bayonet fastener.

FIGS. 14 to 20 show a third practical example of the inventive clampingsystem. The third practical example of the inventive clamping systemdiffers from the first and second practical examples substantially onlyin the configuration of clamping elements 40 of the clamping fork aswell as tightening screw 42. Thus only the differences compared with thefirst practical example will be explained hereinafter.

FIGS. 14 and 15 show the inventive clamping system in the clampedcondition. FIGS. 16 and 17 show the inventive clamping system indetached condition. In FIGS. 18 to 20, the clamping fork of theinventive clamping system is illustrated in various views.

As is evident in particular from FIGS. 18 and 19, clamping elements 40are each provided on the sides of their foot portions 41 connected asone piece with two notches 130 and 132 normal to longitudinal orrotational axis 43 of tool holder 22, the said notches being produced,for example, by milling. Notches 130 and 132 reduce the cross section ofclamping elements 40 compared with the cross sections of clampingelements 40 in the first and second practical example. In the thirdpractical example of the inventive clamping system, portion 131 in theregion of notches 130 functions in particular as a “material articulatedjoint”, which is elastically deformed when the clamping system isdetached, or in other words when the two clamping elements 40 arepinched together as tightening screw 42 is turned. By virtue of thisfeature, which is simple to achieve structurally, the force necessary topinch the two clamping elements 40 together, or in other words to bringthe clamping system into the detached position illustrated in FIGS. 16and 17, is smaller by comparison with the first and second practicalexamples, in which clamping elements 40 are not provided with notches.In order to be able to apply the force necessary to pinch clampingelements 40 together in the clamping system according to the first andsecond practical examples, clamping elements 40 must have a certain“lever length”, considered in axial direction. In the third practicalexample, by virtue of the reduction of the cross section of clampingelements 40 by notches 130 and 132, a smaller force is necessary topinch clamping elements 40 together, or in other words to bring theclamping system into the detached position illustrated in FIGS. 16 and17. If it is required that the same pinching force can be applied on thetwo clamping elements 40 in the clamping system according to the first,second and third practical example by turning tightening screw 42,notches 130, 132 provided on clamping elements 40 of the clamping systemaccording to the third practical example therefore permit considerableshortening of clamping elements 40 and thus of the clamping system onthe whole. Besides the material and weight savings achieved in this wayand the resulting lower manufacturing costs, simpler assembly isadditionally possible by this feature, which is simple to achievestructurally.

Bracing segments 140, which can be seen in FIGS. 14 and 16, are disposedin notches 132. The purpose of bracing segments 140 is to prevent“kinking” of clamping elements 40 in response to a torque, oriented inclockwise direction relative to FIGS. 14 and 16, while the clampingsystem is being clamped, or in other words when clamping elements 40 aremoving apart from one another. In the detached position of the clampingsystem shown in FIG. 16, these bracing elements, which preferably aremade from aluminum or another metal, are freely movable in notches 132.In the clamped position of the clamping system shown in FIG. 16, thesebracing segments 140 are pinched between the flank faces definingnotches 132, thus imparting stiffness to clamping elements 40, so thatneither one can kink “backward” around an imaginary fulcrum representedby the inside circumferential wall portion of guide recess 31 of holdingportion 32 between undercut recess 46 and recess 30 of holding portion32.

A further difference of the clamping system according to the thirdpractical example compared with the clamping system according to thefirst and second practical examples can be recognized in theconfiguration of tightening screw 42. Whereas tightening screw 42 in thefirst and second practical examples is made in one piece with headportion 52 and threaded portion 56, tightening screw 42 according to thethird practical example has two-piece configuration. From FIGS. 14 to 17it follows that tightening screw 42 has a threaded portion 56 with aleft-hand threaded portion 56 b and a right-handed threaded portion 56a, one of which is disposed in threaded bore 62 of upper clamping member38 in FIGS. 14 to 17 and the other is disposed in a nut functioning ashead portion 52 and disposed in recess 57 of lower clamping member 38.The advantage of this configuration is that, by virtue of theleft-hand/right-hand thread of tightening screw 42, relatively smallturning movements are necessary to bring about a relatively large“stroke” of clamping members 38; furthermore, the nut functioning ashead portion 52 is loaded substantially only in tension, and so neitherthe nut nor the corresponding clamping members 38 are subjected tosevere frictional wear. Further refinements of this tightening screw 42according to the third practical example are evident in FIGS. 14 to 17.

Assembly/disassembly of the tool on/from the tool holder as well as themode of operation of the clamping system according to the thirdpractical example take place in principle in the same manner as in theclamping systems according to the first and second practical examples,and so more detailed explanation is not necessary at this place.

Naturally the specific features of the first, second and third practicalexamples can be combined with one another or substituted for one anotheras desired, to the extent that this is technically possible and seems tobe expedient.

The present invention therefore provides a clamping system fordetachably connecting two parts, which preferably are rotationallysymmetric, of which one part has a preferably cylindrical or taperedhollow shank and the other part has a corresponding holding portion forholding the hollow shank in accurately fitting relationship. Theclamping system is provided with a clamping device, which is disposedconcentrically in the holding portion and which, in the joined-togethercondition of the two parts, extends into the hollow shank of the onepart and is provided with at least two clamping members which can movein opposite directions as well as with an actuating device for drivingthe clamping members. The clamping members can be engaged with anddisengaged from an undercut clamping shoulder of the hollow shank,whereby a pressing force is generated between plane faces of the twoparts to be connected. The clamping members are constructed as headportions of elongated clamping elements, which are disposedsubstantially parallel to the longitudinal or rotational axis of theholding portion and the foot portions of which are connected to oneanother.

What is claimed is:
 1. A clamping system for detachably connecting twoparts, of which one part has a hollow shank and the other part has acorresponding holding portion for holding the hollow shank in accuratelyfitting relationship, with a clamping device, which is disposedconcentrically in the holding portion and which, in the joined togethercondition of the two parts, extends into the hollow shank of the onepart and is provided with at least two clamping members which can movein opposite directions as well as with an actuating device for drivingthe clamping members, by means of which device the clamping member canbe synchronously moved into and out of engagement with an undercutclamping shoulder of the hollow shank, whereby a pressing force isgenerated between plane faces of the two parts to be connected, theclamping members being constructed as head portions of elongatedclamping elements, which are disposed substantially parallel to alongitudinal or rotational axis of the holding portion and foot portionsof which are connected to one another, characterized in that theclamping elements are each provided in a region between head and footportions with a retaining portion, which can be brought into engagementwith an undercut recess of the holding portion.
 2. A clamping systemaccording to claim 1, characterized in that the clamping elements havethe form of legs of a U-shaped clamping fork of one-piece structure. 3.A clamping system according to claim 1, characterized in that the footportions of the clamping elements are connected to one another by anarticulated joint, the axis of rotation of which is disposedperpendicular to the longitudinal or rotational axis of the holdingportion.
 4. A clamping system according to one of claims 1,characterized in that the clamping elements are each provided in aregion between head and foot portions with a retaining portion, whichcan be brought synchronously with the engagement of the clamping memberswith the undercut clamping shoulder of the hollow shank into engagementwith an undercut recess of the holding portion.
 5. A clamping systemaccording to claim 4, characterized in that the undercut recess has aclosed annular cross section.
 6. A clamping system according to claim 1,characterized in that the clamping members are each provided with awedge face which cooperates with a mating face provided on the undercutclamping shoulder of the hollow shank.
 7. A clamping system according toclaim 6, characterized in that the undercut clamping shoulder is part ofa recess formed with a closed annular cross section in the hollow shank.8. A clamping system according to claim 1, characterized in that theclamping device is disposed in a corresponding guide recess of theholding portion and at the bottom of the guide recess bears against anannular seal.
 9. A clamping system according to claim 1, by a push-offattachment, which can be actuated axially by the clamping members upondetachment of the engagement with the undercut clamping shoulder, andwhich is used for separation of the two parts to be connected.
 10. Aclamping system according to claim 9, characterized by a push-off pistonas part of the push-off attachment, which piston is disposed in acentral recess in the part supporting the hollow shank and which, whenthe engagement of the clamping members with the undercut clampingshoulder is detached, can be pressed synchronously with increasing forceagainst a bracing face in the recess, whereby a centrally acting,positive force is applied on the part supporting the hollow shank.
 11. Aclamping system according to claim 10, characterized in that, upondetachment of the engagement with the undercut clamping shoulder of thehollow shank, the clamping members move toward one another andsimultaneously travel over a tapered face formed on the push-off piston.12. A clamping system according to claim 9, characterized in that thereis disposed in a circumferential groove of the push-off piston a sealingring, via which the push-off piston bears against the circumferentialwall of the recess.
 13. A clamping system according to claim 1,characterized by a coolant and lubricant supply system, which comprisesa channel portion formed in the part supporting the holding portion, achannel portion formed in the part supporting the hollow shank, and atleast one line portion bridging the clamping device and ensuringfixation of the angular orientation thereof relative to the holdingportion.
 14. A clamping system according to claim 13, characterized inthat the line portion comprises a tube disposed between the parts to beconnected, the end of the tube on the hollow-shaft side being held in acorresponding recess of a push-off piston, the shank portion of the tubebeing guided in axially movable relationship through a correspondingrecess of the connecting portion of the clamping device, and the end ofthe tube on the holding-portion side being held in close-fittingrelationship in a corresponding recess in the part supporting theholding portion.
 15. A clamping system according to claim 13,characterized in that the line portion is positioned between theclamping members in such a way that the clamping members pinch the lineportion when the clamping system is in detached position.
 16. A clampingsystem according to claim 1, characterized in that the pressing faces ofthe parts to be connected are designed as radial annular faces.
 17. Aclamping system according to claim 1, characterized in that theclose-fitting faces between hollow shank and holding portion have theform of tapered faces.
 18. A clamping system according to claim 1,characterized in that the holding portion and the hollow shank are eachprovided with a radial opening oriented perpendicular to thelongitudinal or rotational axis into which a tool can be introduced fromoutside to drive the actuating device.
 19. A clamping system accordingto claim 18, characterized in that the actuating device is a tighteningscrew with a head portion disposed in a corresponding recess of the oneclamping member and a threaded portion disposed in a correspondingthreaded bore of the other clamping member.
 20. A clamping systemaccording to claim 1, characterized in that the clamping device is madefrom a cylindrical part, so that the clamping elements and the clampingmembers have an arcuate outside face and the connecting portion has acylindrical outside face.
 21. A clamping system according to claim 1,characterized in that, when the clamping system is in clamped condition,the portions of the clamping elements adjoining the clamping membersbear against the inside circumferential wall of the guide recess of theholding portion.
 22. A clamping system according to claim 19,characterized in that the threaded portion of the tightening screw has aleft-hand threaded portion and a right-hand threaded portion, of whichone of the right-hand threaded portion and the left-hand threadedportion is disposed in the threaded bore of the other clamping memberand the other of the right-hand threaded portion and the left-handthreaded portion is disposed in a nut functioning as the head portion,the nut being disposed in the recess of the one clamping member.
 23. Aclamping system according to claim 1, characterized in that the clampingelements are each provided on the side of their foot portions with atleast one notch which reduces the cross section.
 24. A clamping systemfor detachably connecting two parts, said clamping system comprising: afirst part having a hollow shank, the hollow shank having an undercutclamping shoulder; a second part having a holding portion configured toreceive the hollow shank, said holding portion having an undercutrecess; and a clamping device disposed within the holding portion andextending into the hollow shank, the clamping device having at least twoclamping members and an actuating device configured to drive the atleast two clamping members into and out of engagement with the undercutclamping shoulder, whereby a pressing force is generated between planefaces of the first part and the second part, the clamping members beinghead portions of elongated clamping elements, the elongated clampingelements having foot portions that are connected to one another, whereinthe elongated clamping elements are provided in a region between headand foot portions with a retaining portion configured to engage theundercut recess of the holding portion.